The effect of harvesting time on some phytochemical characteristics of Cynara scolymus L. leaves

Artichoke (Cynara scolymus L.) is a perennial plant that belongs  belongs to Asteraceae family. It has a special place in the pharmaceutical and food industries in the world. In order to evaluate some phytochemical characteristics of artichoke leaves at different growth stages, an experiment was conducted by using a randomized complete blocks design (RCBD) with three replications in Isfahan Agricultural and Natural Resources center during two consecutive years (2014-2015 and 2015-2016). In the second year, the leaves were collected at three growth stages: vegetative, heading and flowering in the second year. After harvesting, some quality factors such as their total phenolic content (Folin–Ciocalteu method), total flavonoids (Colorimetric Method of Aluminum Chloride), chlorogenic acid content (HPLC method)and antioxidant activity (DPPH free radical scavenging activity and reducing power) were measured. The results showed that the phytochemical and antioxidant properties of artichoke leaves were different at the three growth stages. The highest amount of phenolic content (76.25 mg GAE g-1 DW), total flavonoid (1.28 mg QE g-1 DW), chlorogenic acid content (2.25 % DM), DPPH (92.34 %) and reducing power (2.16) of methanolic extract was observed in heading stage. There was a positive and significant correlation between total phenolic content and antioxidant activity. Also, the relationship between chlorogenic acid content and DPPH and reducing power was positive and significant. According to the results, the harvesting of artichoke leaves at the heading stage is better than other growth stages due to their favorable characteristics.